Process for making permanent magnet alloys consisting of silver, manganese, and aluminum



Patented Apr. 23, 1946 UNITED STAT PROCESS FOR MAKING PERMANENT MAG- NET ALLOYS CONSISTING OF SILVER, MANGANESE, AND ALUMINUM Goodwin H. Howe, Scotia, N. Y., assignor to Generai Electric Company, a corporation of New York No Drawing. Application-July 29, 1943,

Serial No. 496.620

2 Claims. (Cl. 148-115) The present inventionis a process for manufacturing permanent magnet alloys consisting of silver, manganese and aluminum. Magnet of that composition are disclosed in Faus Patent 2,247,804, July 1, 1941, and consist of 2 to 8% aluminum, to 15% manganese with theremainder substantially all silver. A preferred alloy consists of about 86.5% silver, 8.8% manganese and 4.7% aluminum, The very high coercive force possessed by such alloy magnets makes them desirable forus in many fields, for example in maintaining polarity in reverse current relays and as control magnets for moving magnet instruments and the like.

It is an object of the present invention to provide a process for improving the magnetic propto efiect a condition of solution in the alloyandthen water quenched from that temperature. Thereafter the alloy rods are cold reduced by swaging'to a diameter of about /2" which constitutes a reduction in cross sectional area of about 55%. The alloy rods are then given a homogenizing treatment at about 760 C., the

heating period again varying from about one-half to one hour, "quenched therefrom and then further cold reduced by swaging to a final diameter of about .410 inches, a reduction of about 35% in cross sectional area. Thereafter the alloy is artificially aged at about 250 C. the aging period varying from about 36 to '72 hours. Permanent magnets .410" in diameter and .156" long andv consisting of the above-noted preferred alloycomposition and roduced in accordance with the above process have a total flux of about 1'70 lines and are of uniform quality whereas magnets of the same size produced in accordance with the prior art process have a total flux-of about 156.

If a higher total flux is required, the above process may be varied slightly with respect to .the amount of cold reduction applied to the alloy and the aging process. For. example, the alloy is given the usual solution treatment at 760 C.,'

quenched from that temperature, then cold reduced about 60 to 65% by swaging, given the homogenizing treatment at 760 (3., water quenched therefrom and aged at 250 C. for about 48 hours. The alloy is then given a further cold reduction of about to and again aged at about 250 C. for about 48 hours. With this modifled process it is possible to obtain in permanent magnet alloys having the above-noted preferred composition. a total flux value of 190 to 200 in magnets .410" in diameter and .156" long. Magnets of the above composition treated in this manner also have a Br of 747, all-1e of 5840, and a BHmax. of 2,075,000. v

In heating the alloy to effect the solution condition therein the temperature should not exceed 800 (3., and preferably should be maintained at about 760 C. for best results. Although I prefer to maintain the alloy at the solution temperature erties of such alloys and particularly to provide The -' lurgically and magnetically than would be possifor one-half to one hour, the desired eflect might be obtained in as short a time as 15' minutes. Although heating the alloy at the solution temperature for a longer period of time than one hour does not have any adverse efiect it also does not have any advantage. The aging temperature employed in my process preferably is about 250 C. and this temperature should not be varied greatly. The aging period, however, may be varied. Preferably, however, it should be maintained for about 36 to 72 hours. By homogenizing the present alloy it is possible toobtain a magnet which has better magnetic properties and which is more stable both metalble without such treatment.

The total cold reduction in cross sectional area of the alloy by cold swaging preferably should amount to about although good results may be obtained with a total cold reduction in area varying from about 50 to While good properties may be obtained in the alloy if the cold reduction is effected by a rolling operation, the maximum magnetic properties which are obtained by cold swaging the alloy cannot be duplicated by cold rolling unless the rolling operation is employed to produce very thin material, for example strip about in thickness. In rolling,

the alloy is free to flow in a perpendicular direction aswell as in, the rolling direction ,while in swaging the alloy is severely strained since it can flow only in one direction which accounts for the improved magnetic properties obtained through swaging. The cold reduction of the alloy may be effected either by flat rolling, rolling with grooved rolls or by swaging, the latter being the preferred method except for the production ofvery thin material where flat rolling should be employed.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A method for improving the permanent magnet properties or an alloy containing about 2 to 8% aluminum, 5 to 15% manganese with the remainder substantially all silver, which comprises heating the alloy at about 160 C. until a condition of solution is eflected in the alloy, quenching the alloy from that temperature, wasing the alloy to effect a cold reduction in cross sectional area thereof of about 55%, reheating the alloy at about 760 C. and quenching therefrom, further cold reducing the alloy about 35% in cross sectional area and thereafter aging the alloy at about 250 C.

2. A method for improving the permanent magnet properties or an alloy containing about 2 to 8% aluminum, 5 to 15% manganese with the vremainder substantially all silver, which comprisesheating the alloy at about 760 C. for a period of about one-half to one hour, quenching the alloy from that temperature, cold swaging the alloy. to reduce its cross sectional area about 55% homogenizing the alloy at 760 C. and quenching thereirom, again cold swasing the alloy to efiect a reduction of about 35% in cross-sectional area thereof and finally aging said alloy at a temperature of about250 C. for about 36 to '72 hours. GOOD'WIN H. HOWE. 

